Displaying Loops

McIDAS can display an automatically repeating sequence of frames much like a movie loop.

Defining Loops

Define the sequence of frames using either the LS or LB command. Command DR determines the amount of time that each frame is displayed.

Once a loop is defined, use the single-letter commands L, A and B to control the state of the display.

L starts and stops the loop. If the loop is actively stepping through frames, pressing Alt L stops on the first frame of the loop. Similarly, if looping is inactive, pressing Alt L starts the animation.
A manually advances one frame while the loop is stopped.
B command backs up one frame while the loop is stopped.

In sessions with independent graphics, the Y and J commands toggle image and graphics frames to and from the loop control system. If Y is toggled on, image frames step through their LB or LS sequence when looping is started with the L command. If Y is toggled off, the displayed image frame does not change when looping is started. The J command controls graphics frame looping in the same way. At startup, Y is on and J is off, meaning that only image frames are looped with the L command.

Saving and Recalling Loops

After you define a loop or display using the commands described above, use the DEFLOOP command or the F Key Menu System pseudocommand *Snn to save it. You can define up to 99 loops. For more information, see Chapter 5, F Key Menu System, or DEFLOOP in Chapter 3, Commands.

Display saved loops in the Image Window using a defined function key, or using the MOVIE or DEFLOOP REST command. The MOVIE command automatically steps through predefined loops at user-defined rates.

Using Briefing Windows

In addition to displaying loops in the Image Window, you can also create briefing windows to view saved loops. Each briefing window can display a frame or loop different than those currently shown in the Image Window or other briefing windows.

Use the command BRIEF to create a briefing window. You can create up to ten additional briefing windows to display the loops. If you resize a briefing window, its displayed frames are automatically rescaled to fill the window.

You can only display loops 1 through 9 in a briefing window. Use the MOVIE command with the WIN keyword, or make the briefing window active and press a key between 1 and 9 that corresponds to the loop number. Use the A, B and L keys in briefing windows to control frame stepping.

Use the SYNC command to define and display frame sequences in multiple briefing windows. The loops are synchronized, making it easier to compare loops of visible and infrared satellite imagery, for example.

Automatically Updating Loops

If you have access to a server ingesting images in real time, you can use the SKE, SKL and SKU scheduler commands with the IMGDISP command to automatically display the latest image in a loop of frames. You can also adjust the loop's dwell rates or frame sequence to emphasize the new image. Two methods are available to do this.

You can run the DR AUTO command after each new image is displayed. This command rotates the dwell rates, assigning the longest dwell to the most recent image in the loop.

Or, you can define the loop's frame sequence using the LS command with the UPDATE=Y keyword, which automatically rotates the frame sequence each time a new image is displayed with IMGDISP. The new image moves to position 1 in the loop. Dwell rates are not changed, so the new image has the dwell initially set for position 1. The advantages of this method are that you only run the LS command once, and that the new image is displayed if you stop the loop with the L command.

Optimizing the Loop Display

McIDAS-X has configuration options that determine the quality of frame looping. The options are the -optimizeForSpeed or the -optimizeForSpace start-up flags. See the section titled Configuring McIDAS-X Sessions with .mcidasrc for more information.

Although McIDAS-X allows frames of different sizes in any session, you should make all frames in the loop bounds the same size when using the L command for looping. Different size frames display poorly and are handled roughly by the window manager.

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